JPS6325399Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an automatic braking gap adjustment device for a hydraulically operated brake.

The invention is particularly applicable to, but not limited to, drum brakes. As is well known, a drum brake has a pair of arcuate brake shoes on a back plate, one end of which is a fulcrum, and the other end of which is expandable by the operation of a wheel cylinder. Braking is achieved by pressing the brake lining against the circumferential surface. When the brake lining wears out due to this braking, the braking gap between the brake lining and the inner peripheral surface of the brake drum increases.
An automatic braking gap adjustment device provided separately from the wheel cylinder is operated to expand the brake shoe so that the braking gap is always constant.

The applicant previously proposed that the automatic braking gap adjustment device, which is provided separately from the wheel cylinder that expands the brake shoe, is built into the wheel cylinder, has a simple structure, can be manufactured at low cost, and has a spring retainer. By using this, we have provided an automatic braking gap adjustment device for hydraulically operated brakes that ensures the screwing out of the adjustment bolt, has a simple locking structure for the adjustment nut, and is easy to assemble. −148121).

The structure of this device is that a piston is slidably inserted into a cylinder, a hydraulic chamber is defined in the cylinder by the piston and an opposing part of the piston, and a hydraulic pressure chamber is formed between the piston and this opposing part. An adjusting nut and an adjusting bolt which are threaded together are arranged, the clutch part of the adjusting bolt is brought into contact with the clutch surface of the opposing part, and the adjusting nut is attached to a spring having a spring seat part and a plurality of leg parts. The legs of the retainer are fitted into the notches formed in the adjustment nut, and the retainer is further engaged and installed in the communication holes formed in the piston, and the spring is compressed between the spring seat and the adjustment nut. As a result, when the piston is brought into contact with the piston and a braking gap greater than a predetermined value is generated, the adjustment bolt is screwed to move the piston forward, so that the braking gap is always constant.

However, in the automatic braking gap adjustment device configured as described above, it is necessary to remove burrs caused by the threading of the female thread of the adjustment nut, and for this purpose, the area around the opening end of the screw hole on the contact surface of the adjustment nut with the piston is scraped off, and a recess is created around the opening end of the screw hole. It is formed. When the above-mentioned device is assembled and brake fluid is introduced into the hydraulic pressure chamber in the wheel cylinder, air remains in the recess due to the contact between the adjuster nut and the piston, and it is extremely difficult to remove the residual air. .

The present invention has been made to solve this problem, and includes an adjusting nut and an adjusting nut screwed together with a multi-thread screw in a hydraulic pressure chamber defined by a piston slidably inserted into a cylinder and its opposing part. The adjusting nut is held on the piston, and when a braking gap of a predetermined value or more is generated, the adjusting bolt is screwed. In an automatic braking gap adjustment device for a hydraulically operated brake that moves a piston forward, a spring retainer including a spring seat and a plurality of legs is inserted into a notch formed in an adjustment nut. , and is attached to the communicating hole formed in the collar of the piston, and a spring is compressed between the spring seat and the adjustment nut to bring the adjustment nut into contact with the piston, and further, the adjustment nut is attached to the piston side of the piston. A recess is formed between the opening end of the adjustment bolt screw hole and the communication hole to communicate the piston side hydraulic pressure chamber defined by the piston collar and the adjustment bolt side hydraulic pressure chamber. The hydraulically operated brake is equipped with an automatic braking gap adjustment device, and its purpose is to securely prevent the adjustment nut from rotating, prevent air from remaining as mentioned above, and create a fluid that always has good braking performance. An object of the present invention is to provide a braking gap automatic adjustment device for a pressure-actuated brake.

Hereinafter, an embodiment in which the present invention is applied to a two-leading type drum brake will be described with reference to the drawings.

Figures 1 and 2 show an embodiment of the present invention, in which a pair of upper and lower wheel cylinders 1 (the lower part is not shown) are mounted on the inner surface of a back plate (not shown) that is fixed to the vehicle body. ), and a pair of left and right brake shoes 2, 2 are respectively arranged symmetrically around the center of the back plate.

The wheel cylinder 1 is composed of a cylinder body 3 having a cylinder hole 3a with only one end open, and a single piston 5 that slides into the cylinder hole 3a to define a hydraulic chamber 4.The cylinder body 3 has a back plate. is fixed to. A retainer 6 is provided at the outer end of the cylinder body 3, and an engagement groove 5a is formed at the outer end of the piston 5, with which the corresponding ends of the brake shoes 2, 2 are engaged. ing. This retainer 6 and the engagement groove 5
Relative rotation between the cylinder body 3 and the piston 5 is prevented by the engagement between the cylinder body 3 and the brake shoes 2, 2.

The wheel cylinder 1 is provided with a hydraulic pressure introduction port 7 for introducing the output hydraulic pressure of a brake master cylinder (not shown) into the hydraulic pressure chamber 4 thereof.

In the hydraulic chamber 4 of the wheel cylinder 1, an automatic braking gap adjustment device A of the present invention is arranged in series with the piston 5, which will be described in detail below.

The piston 5 has a collar portion 9 at the tip of the small diameter portion 8, and the collar portion 9 defines a hydraulic pressure chamber 4 on the piston cup 11 side and a hydraulic pressure chamber 4 on the adjuster bolt 19 side, which will be described later. , and a piston cup 11 is fitted into a cup groove 10 formed in the small diameter portion 8. The collar 9 at the tip of the piston 5 is formed with a recess 12 extending in a trifurcated shape from the center.By forming this recess 12, a substantially arcuate communication hole 13 is formed in the collar 9. It is formed in places. The adjusting nut 15 has a collar portion 15a.
The adjusting nut 15 is placed in contact with the contact surface 14 of the piston 5 so as to be able to separate from the adjusting nut 15, and the adjustment nut 15 is prevented from rotating by the collar portion 9 of the piston 5 by a spring retainer 16, and is held under pressure by a spring 17. . This adjustment nut 15 has a notch 18 formed in the collar 15a at a position corresponding to the communication hole 13 formed in the collar 9 of the piston. Further, on the contact surface 15b of the adjusting nut 15 with the piston 5, there is a recess 15d around the open end of a screw hole 15c into which an adjusting bolt (to be described later) is screwed, for scraping off burrs generated when the screw hole is threaded. is formed. On the other hand, the spring retainer 16 includes a spring seat portion 16a and three leg portions 16c each having a locking claw 16b at the tip.

The piston 5, adjuster nut 15, spring retainer 16 and spring 17 are assembled as follows. First, attach the collar 15 of the adjuster nut 15 to the contact surface 14 of the piston 5.
a to align the communication hole 13 and the notch 18 and bring them into contact with each other. Next, the spring 17 is interposed between the adjuster nut 15 and the spring retainer 16, and the leg portion 16c of the spring retainer 16 is inserted.
into the notch 18 of the adjusting nut 15, and insert the locking pawl 16b into the communication hole 13 of the piston 5.
to be locked. The spring 17 is compressed between the collar portion 15a of the adjuster nut 15 and the spring seat portion 16a of the spring retainer 16.

The adjuster nut 15 assembled in this way resists this spring 17 and is attached to the piston 5.
Although it can be separated from the abutting surface 14 of
It is stopped from rotating.

An adjustment bolt 19 is screwed into the shaft portion 15e of the adjustment nut 15 via a multi-start thread portion 19a so as to pass through a screw hole 15c at the center thereof. The threaded portion between the adjusting nut 15 and the adjusting bolt 19 is provided with an appropriate braking gap between each brake shoe 2, 2, that is, an appropriate gap between each brake shoe 2, 2 and a brake drum (not shown). An axial backlash is set.

A clutch portion 1 is attached to the end of the adjuster bolt 19.
9b is formed, and this clutch portion 19b
is rotatably fitted into a cylinder small diameter section 20 provided on the inner end wall of the cylinder body 3, and faces a conical clutch surface 21 formed on the back wall of the cylinder small diameter section 20. And adjust bolt 1
A sealing member 22 is fitted into the sealing groove 19c of 9 to prevent the hydraulic pressure in the hydraulic pressure chamber 4 from acting on the clutch surface 21.

Next, the operation of this embodiment will be explained.

When brake fluid is introduced from the hydraulic pressure introduction port 7 into the hydraulic pressure chamber 4 in the wheel cylinder 1 which incorporates the automatic braking gap adjustment device A assembled as described above, as the brake fluid fills the hydraulic pressure chamber, the hydraulic pressure increases. The air in the pressure chamber is discharged from the brewer (not shown),
At this time, the air in the recess 15d formed in the above-mentioned adjusting nut 15, although the adjusting nut 15 comes into contact with the collar 9 of the piston 5, the center portion 12a of the collar 9 is in contact with the recess of the adjusting nut 15. 15d and communicates with the hydraulic pressure chamber 4 through the extension 12b, the liquid is guided to the hydraulic pressure chamber 4 through the recess 12 and discharged from the brewer. becomes. At this time, in this embodiment, at least two of the recesses 12 having a trifurcated shape extending from the center are
Since the two extending portions 12b are formed in the same direction as the engagement groove 5a of the piston 5, when the piston is assembled, one of the extending portions 12b is always positioned facing upward. do. Therefore, the air remaining in the recess 15d of the adjusting nut 15 is guided to the hydraulic chamber 4 very easily.

When braking is not performed, the return spring force is applied to the piston 5 via the brake shoe 2.
This is transmitted to the adjusting nut 15 and the adjusting bolt 19, and enters the clutch surface 21 of the clutch portion 19b, generating clutch torque. At this time, since the adjusting nut 15 and the adjusting bolt 19 are threaded together with a multi-thread thread, rotational torque is generated in the adjusting bolt 19, but the clutch torque is set to be larger than this adjusting bolt rotational torque. Therefore, the adjuster bolt 19 does not rotate and the piston 5 maintains its position.

Next, in order to perform braking, a master cylinder (not shown) is actuated to introduce pressure fluid from the hydraulic pressure introduction port 7 into the hydraulic pressure chamber 4. When the piston 5 moves forward in the axial direction, the brake shoe 2 is transferred to the wheel. The braking action is performed by pressing against the inner peripheral surface of the brake drum, which rotates together with the brake drum.

By the way, when the brake lining is not worn to a predetermined level or during braking immediately after adjusting the braking gap, as the piston 5 moves forward, the adjuster nut 15 is brought into contact with the collar portion 9 by the elastic force of the spring 17 via the spring retainer 16. It moves together with the piston 5 while maintaining its state. Since the amount of movement of the adjusting nut 15 is the amount of movement corresponding to back crushing, no rotational torque is generated in the adjusting bolt 19 which is threaded with a multi-thread screw, and the adjusting nut 15 is not adjusted. When the brake is released, the piston 5 and adjustment nut 15 return to their original positions together.

In this normal braking state, the hydraulic pressure in the hydraulic pressure chamber 4 is relatively low, and therefore the frictional coupling force between the clutch portion 19b of the adjusting bolt 19 and the clutch surface 21 of the cylinder small diameter portion 20 is relatively small. Therefore, if the piston 5 moves further outward due to wear of the brake linings of the brake shoes 2, 2, the adjustment nut 15 will be brought into contact with the contact surface 14 by the elastic force of the spring 17 via the spring retainer 16. Piston 5 while maintaining contact state.
move with

This amount of movement is equal to the amount of wear on the brake lining added to the backlash, and since the movement is greater than the backlash, the adjusting bolt 19 moves together with the adjusting nut 15, and the clutch portion 19b of the adjusting bolt 19 is connected to the cylinder. away from the clutch face 21 of the small diameter portion 20. The adjustment nut 15 is pressed against the contact surface 14 of the piston 5 by the elastic force of the spring 17, and its rotation is restricted by the legs 16c of the spring retainer 16. Rotational torque is generated at the threaded part of the multi-thread screw. This allows the adjustment bolt 19
moves toward the clutch surface 21 while twisting around the adjuster nut 15, and engages with the clutch surface 21 again. In this way, a self-adjusting action is carried out to compensate for wear on the brake linings of the brake shoes 2,2. Here, if the pressure inside the hydraulic chamber 4 is reduced to release the brake, the brake shoe 2,
2 contracts in response to the returning force of the return spring, and this returning force acts on the piston 5, the adjusting nut 15, and the clutch part 19b of the adjusting bolt 19 as a thrust toward the clutch surface 21, and as a result, the clutch part 19b It is frictionally coupled to the clutch surface 21, making it impossible for the adjustment bolt 19 to rotate. Therefore, the piston 5 and the adjusting nut 15 can only move backward by a stroke corresponding to the backlash of the threaded portion of the adjusting bolt 19, and as a result, the brake lining of each brake shoe 2 and the inside of the brake drum are damaged. An appropriate braking gap corresponding to the backlash is created between the brake and the circumferential surface.

In addition, when strong braking is performed, the hydraulic pressure in the hydraulic pressure chamber 4 rises to a predetermined value that causes elastic deformation in the brake shoes 2, 2, brake drum, etc., as described above. A self-adjusting action is performed. When the hydraulic pressure exceeds the predetermined value,
The thrust due to the hydraulic pressure of the clutch portion 19b of the adjusting bolt 19 increases, and the clutch portion 19b
Since the adjusting bolt 19 is held in a frictionally connected state with the clutch surface 21, the adjusting bolt 19 cannot rotate. Therefore, the unrotatable adjusting nut 15 is fastened on the adjusting bolt 19 by the legs 16c of the spring retainer 16, so that when the piston 5 moves further outward due to elastic deformation of the brake drum, etc., the spring 17 By deflecting, the adjusting nut 15 maintains its position together with the adjusting bolt 19, and the abutment surface 14 of the piston 5 is separated from the adjusting nut 15. In this way, the automatic adjustment action is stopped.

FIG. 3 shows another embodiment of the present invention, in which the recess 12 is provided in the collar 9 of the piston 5 in order to communicate the recess 15d of the adjuster nut 15 with the hydraulic chamber 4. In contrast, in this embodiment, a circular recess 15b connecting the recess 15d and the notch 18 is formed on the contact surface 15b of the adjuster nut 15 with the piston 5.
The operation is the same as in the previous embodiment.

In this embodiment, the spring is compressed between the adjuster nut and the retainer, but the separate spring can be omitted by providing the retainer itself with spring properties.

As described above, the present invention includes a spring retainer having a spring seat and a plurality of legs, the legs of which are fitted into notches formed in an adjuster nut, and inserted into communication holes formed in the collar of a piston. In addition to being locked and installed, the spring is compressed between the spring receiving seat and the adjusting nut to bring the adjusting nut into contact with the piston, so the adjusting nut and adjusting bolt can be assembled easily and reliably. A recess between the opening end of the screw hole for the piston-side adjustment bolt of the adjustment nut and the communication hole, which communicates the piston cup-side hydraulic pressure chamber defined by the piston collar with the adjustment-bolt side hydraulic pressure chamber. Because of this, when brake fluid is introduced and filled into the hydraulic pressure chamber in the wheel cylinder, it is possible to prevent air from remaining in the recess that inevitably occurs during the process of forming the threaded hole of the adjuster nut, resulting in a more perfect and quick process. Since it is possible to bleed air and also ensure that the adjuster nut is prevented from rotating, it is possible to provide a brake that always has good braking ability while being equipped with a sophisticated and excellent braking gap automatic adjustment device. In addition, the recessed portion, together with the communication hole formed in the piston, further improves the communication between the adjusting bolt side hydraulic pressure chamber and the piston cup side hydraulic pressure chamber, and the air removal from the piston cup side hydraulic pressure chamber is also significantly improved. do. Furthermore, the structure is simple, and the piston, adjuster nut, etc. can be easily molded, so it is extremely easy to implement, and has various other effects.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, in which FIG. 1 is a cross-sectional front view of the main parts, FIG. 2 is an exploded perspective view of the components of the automatic braking gap adjustment device, and FIG.
The figure is a sectional front view of main parts showing another embodiment. 1 is the wheel cylinder, 2 is the brake shoe,
3 is the cylinder body, 4 is the hydraulic chamber, 5 is the piston,
9 is a collar, 12 is a hole, 13 is a connecting hole, 15 is an adjuster nut, 16 is a spring retainer,
17 is a spring, 18 is a notch, 19 is an adjustment bolt, 19b is a clutch, 20 is a cylinder small diameter portion, and 21 is a clutch surface.

Claims (1)

[Scope of utility model registration request] An adjustment nut and an adjustment bolt screwed together with a multi-start thread are arranged in series with the piston in a hydraulic pressure chamber defined by a piston slidably inserted into the cylinder and its opposing part. The clutch surface of the bolt is brought into contact with the clutch surface of the opposing portion, while the adjusting nut is held on the piston, and when a braking gap of a predetermined value or more is generated, the adjusting bolt is screwed to move the piston forward. In an automatic braking gap adjustment device for a type brake, a spring retainer including a spring seat and a plurality of legs is fitted into a notch formed in an adjustment nut, and the legs are fitted into a notch formed in a piston collar. At the same time, the spring is compressed between the spring seat and the adjusting nut to bring the adjusting nut into contact with the piston, and the opening end of the screw hole for the adjusting bolt on the piston side of the adjusting nut is installed. A hydraulically operated brake characterized in that a recess is formed between the communication hole and the piston cup side hydraulic pressure chamber defined by the collar of the piston and the adjustment bolt side hydraulic pressure chamber. automatic braking gap adjustment device.